Huddle Up: the Surprising Physics of Penguin Movements

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When male emperor penguins face the minus-58-degrees-Fahrenheit
(minus 50 degrees Celsius), 120-mph (200 km/h) winds of Antarctic
winters, the birds rely on their neighbors' bodies to keep
themselves — and the eggs that they protect in a pouch near their
feet — alive and warm.

Maintaining a massive
huddle of thousands of penguins may sound fairly simple, but
sticking together in a pack so large turns out to be quite
complicated: When one penguin moves a single step, the rest must
also move to accommodate the open space and stay warm. In
this particular species of penguin, males play the unusual gender
role of incubating eggs, so it is especially crucial that they
maintain warmth during cold winters.

Previous research has suggested that
individual penguins within a huddle regularly make small
movements roughly every 30 to 60 seconds, travelling between 2
and 4 inches (5 and 10 centimeters) with each step. But
researchers haven't understood the physics behind how all of
these moving parts stick together as a single unit.

The team's mathematical models showed that the huddles behave as
waves instigated by any individual in the pack, no matter that
individual's location. If two waves travel toward each other,
they merge, rather than passing one another. Gaps just 2
centimeters wide (0.8 inches) appear to instigate a
reorganization, in order for the penguins to stay warm, the team
reports today (Dec. 16) in the New Journal of Physics.

Why penguins move so frequently and in such small steps remains
unclear, though the researchers think the shuffles may help the
birds rotate their eggs to keep them warm.

"It might be that the egg can get cold at the bottom and so the
penguins have to rotate the egg every now and then," Gerum said.
"This is just a speculation."

Emperor penguins are the only vertebrates on the Antarctic
continent that breed during the coldest months of the year.

While the model that the researchers created has the penguins
moving in a straight line, the natural formation of the huddles
often moves more in a spiral rotation, Gerum said. Next, the team
hopes to create a mathematical model that recreates this more
complicated rotational movement.